Integral centraliser

ABSTRACT

A method of providing at least one projection ( 4 ) on a tubular body ( 1 ) of the type required by the oil and gas industry for use in recovery of and transporting of crude oil or gas, namely oil-country-tubular goods (OCTG), said projection ( 4 ) having a predetermined form such as a blade, ribbing, or the like stand-off projection, by providing materials capable of being moulded, applying a mould to a tubular (OCTG) body, and moulding said materials using said mould onto said tubular body ( 1 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Ser. No. 13/461,583 filed May1, 2012, the entire content of which is incorporated herein byreference. U.S. Ser. No. 13/461,583 is a Continuation application ofU.S. Ser. No. 10/524,371 filed Feb. 10, 2005, which is a National Stageof PCT Application No. PCT/IT02/00536 filed Aug. 12, 2002.

This application relates to tubular products of the type required by theoil and gas industry for use in recovery of an transporting of crude oilor gas, namely oil-country-tubular goods (OCTG), particularly a tubularproduct adapted to be inserted downhole in a centralized position.

The use of centralizing means for aligning a tubular product(hereinafter “tubular”) within a well bore is well known in the field. Atypical centralizer (or centralizer) takes the form of an open-endedsubstantially cylindrical hollow body to be attached as a close-fittingsleeve or collar around a tubular. The body is provided with radiallyprojecting parts such as ribbing or spaced apart blades so that fluidpathways are defined between the projecting parts permitting fluids topass around the centralizer when it is located in the bore. Theprojecting parts provide lands for engagement of downhole surfaces toprovide a means of making the tubular stand-off to its intendedcentralised position. The design of the projecting parts varies fromaxially aligned “vertical” blades through off-set-straight to helical or“spiral” patterns, and continuous or interrupted (slotted) blade designsoften with bevelled ends. The lands may be so designed that in situdownhole they are used to divert the tubular to follow a deviation inbore path, and so design specification for one centraliser may alsodiffer in this respect from that of another centraliser.

Whilst numerous types of centralisers are known, the common purpose fora typical centraliser is that it is intended to be located on a tubularbody such as casing, pipe, or similar conduit, or a tool to be installedin a bore hole, and is retained in a desired axial position on thetubular by fasteners, stop collars, welding, cementing, or by use ofadhesive or simply frictional engagement over the tubular. Certain typesof centralisers are of the “rotating” type which are fixed onto atubular body to turn with the tubular, and others are of the“non-rotating” type which are axially retained on the tubular, but areequipped with roller devices so that when the lands thereof engagewithin the bore, the tubular will rotate within the centraliser.

The known centralisers are in the main made from metal, such asaluminium, steel, and zinc, typically nowadays by casting methods butpossibly by extrusion, and recently special alloys have become popularfor special purposes, e.g. zinc alloys and bronze alloys. There havebeen also proposals for centralisers made of, or including plastics,e.g. durable plastic resins such as NYLON, and TEFLON. Use of specialmaterials for the surfaces of the lands has been proposed, includingzirconia, titania, alumina and metal carbides.

Reference may be made to the patent literature to obtain more details ofthe centralisers previously proposed for use in this industry. Britishpatent publications in this field include: GB-A-2 016 063, GB-A-2 148984, GB-A 2 148 985, GB-A-2 155 519, GB-A-2 171 436, GB-A-2 197 008,GB-A-2 201 176, GB-A-2 210 084, GB-A-2 210 085, GB-A-2 230 808, GB-A-2241 009, GB-A-2 242 457, -GB-A-2 249 333, GB-A-2 252 118, GB-A-2 253428, GB-A-2 272 233, GB-A-2 277 336, GB-A-2 282 615, GB-A-2 285 649,GB-A-2 290 331, GB-A-304 753, GB-A-2 316 422, GB-A-2 331 534, GB-A-2-329209, and GB-A-2 339 584. Other patent publications, of which only a feware mentioned here include: EP-A-0 125 993, EP-A-O 143 219, EP-A-O 196339, EP-A-O 410 729, EP-A-O 506 663, EP-A-O 512 154, EP-A-O 585 315,EP-A-0 671 546, EP-A-O 816 628, EP-A-O 830 492, EP-A-O 920 569, EP-A-O996 811, EP-A-1 047 859, WO 91/05 093, WO 98/07953, WO 98/37 302, WO98/37 881, WO 98/40 601, WO 98750669, WO 99/04132, WO 99/24690, WO99/25949, WO 99/36660, WO 99/36661, WO 99/48443, WO 00/66874, U.S. Pat.No. 4,077,470, U.S. Pat. No. 4,363,360, U.S. Pat. No. 5,005,642, U.S.Pat. No. 5,095,981, U.S. Pat. No. 5,332,049, U.S. Pat. No. 5,335,723,U.S. Pat. No. 5,797,455, U.S. Pat. No. 5,810,100, U.S. Pat. No.5,937,948, and U.S. Pat. No. 6,006,830.

It is observed that in practice many of the known centralisers have apreferred orientation for installation in service and are often markedwith symbols e.g. arrows to aid the installer. Even so it is often thecase that the centralisers are accidentally inverted duringinstallation, and whilst in many cases this has no serious operationalconsequence, in the case of the more complex designs, incorrectinstallation can affect the passage of fluids past the centraliser andthus reduce performance.

As in most industries, time and labour represent an inevitable aspect ofcosts that ultimately affect operational viability and pricing ofproduct to the consumer. Therefore, any improvements that can be made toreduce the time and or labour involved in on-site tasks have an economicimpact on production. Improvements in this area can also provideimprovements in efficiency and safety. These demands of time and labouragainst productivity are particularly acute in the-mineral oil and gasindustries.

Accordingly, this invention seeks to provide improvements in theinstallation of tubulars for use in a well bore. Thus an object of thepresent invention is to obviate or mitigate at least some of theproblems that have been observed with the provision of centralisers fortubulars as known in the prior art.

The invention provides according to a first aspect of the invention, amethod of providing at least one projection on a tubular body, saidprojection having a predetermined form such as a blade, ribbing, or thelike stand-off projection, by providing materials capable of beingmoulded, applying a mould to a tubular body, and moulding said materialsusing said mould onto said tubular body.

An advantage of this method is that it is thereby possible to providewhatever contours of shape or configuration are required for thecentraliser by simply designing an appropriate mould cavity for thedesired projecting stand-off parts. In this way, it is possible toobtain after the moulding operation upon the tubular the desiredcombination of raised parts such as blades, ribs, bands andcorrespondingly between such parts the required forms of fluid pathwaysin the form of channels, flutes etc. which define recesses with respectto lands formed by the outer surfaces of the projecting parts.

Thus according to another aspect of the invention, there is provided atubular body, having moulded thereto, in a predetermined position, atleast one projection having a predetermined form such as a blade,ribbing, or the like stand-off projection.

Preferably, the method comprises providing composite resin materialsloaded with hard particles, and applying the materials directly to anexterior surface portion of a tubular body by means of a mould, andcuring the resin materials to provide at least one projection of apredetermined size and shape conforming to the design of the mouldpattern.

Preferably, the mould comprises a plurality of cavities adapted to mouldmaterials to a selected shape and size, said cavities being arranged inmould parts capable of being applied around a curved surface to enable atubular body to have radially projecting parts moulded thereon.

The selective positioning of the mould permits selective location ofstand-off parts on the tubular, and it is thereby possible tocontemplate infinite variations for design of tubulars having integralcentralising or stand-off structures. Blades extending radially withrespect to the longitudinal axis of a tubular, for example, may beprovided at circumferentially mutually spaced positions uniformly arounda tubular such that they are all generally within a discrete cylindricalcentralising zone defined around the tubular. Alternatively, thestand-off parts formed by moulding may be in staggered positions, forexample, forming upon the tubular off-set or spiral arrangements ofcentralising or stand-off structures.

Thus the invention enables a prefabricated tubular to be provided forsubsequent use in the field, said prefabricated tubular beingcharacterised by integral centraliser formations, said formations beingformed as projections moulded directly onto the tubular body.

The tubular body with integral centraliser is preferably formed byproviding a resin-ceramic composite material e.g. as powders, particles,fibrils, chopped fibres, beads or the like mouldable particulates,optionally including fillers or other moulding auxiliaries, and meansfor curing or setting the resin into a moulded form.

The resin material may include bonding agents such as an adhesive or thelike curable component, whilst other components to be mixed therewith,whenever moulding is to be carried out may include a hardener,accelerator or curing initiator. The resin-ceramic composite materialmay also include a catalyst to initiate curing of the resin-ceramiccomposite. The catalyst may be thermally activated. Alternatively, themixed materials may be chemically activated by a curing initiator.

The moulding operation may comprise applying an appropriately contouredmoulding part to a tubular body, loading the mould with resin-ceramicmaterials in predetermined amounts to form the desired composite,suitably by injecting the materials into the mould, curing the materialsin the mould, and removing the mould parts to leave the desired mouldedpart formed on the tubular body.

The composite forming materials may be appropriately mixed by use of apre-calibrated mixing and dosing equipment.

The prefabricated tubular with integral moulded centraliser featuresobtainable according to the invention may be further treated afterremoval of the mould parts, e.g. by coating with resins, paints, orbonding of land surface finishing agents thereto.

According to a further aspect of the invention, a composite centraliserfor installation on a tubular (OCTG) comprises a tubular core adapted tobe installed on a tubular in a manner such as to permit rotation of thetubular within the core in use, said tubular core having mouldedthereto, in a predetermined position, at least one projection having apredetermined form such as a blade, ribbing, or the like stand-offprojection.

Such a composite centraliser is provided according to a further aspectof the invention, by a method comprising the selection of a tubular coresuitable for installation around an OCTG tubular, and providing at leastone projection on said tubular core, said projection having apredetermined form such as a blade, ribbing, or the like stand-offprojection, by providing materials capable of being moulded, applying amould to the tubular core, and moulding said materials using said mouldonto said tubular core. Such projections provide lands for surfaceengagement downhole.

The ability of the core to permit the OCTG tubular to rotate down-holeis achievable in an analogous fashion to the so-called “non-rotating”centralisers of the prior art, for example, by providing axial retentionmeans to locate the composite centraliser upon the OCTG tubular, so thatwhenever the lands of the moulded projection(s) engage a surface withina bore-hole, the composite centraliser thereby becomes static and theOCTG tubular remains free to turn within the composite centraliser, andthis may be facilitated by lubrication or roller device modificationsaccording to the prior art. The composite centraliser is installed byaxially aligning the tubular with respect to the composite centraliserand inserting the end of the tubular into the core of the compositecentraliser and working the centraliser along the outer surface of thetubular until it is located in the desired axial position.

One way of achieving performance of the invention will now beillustrated, by way of example only, with reference to the accompanyingdrawings in which:

FIG. 1 is a plan view of a mould part;

FIG. 2 is a side view of hinged mould parts in an opened position;

FIG. 3 is a section through a tubular around which the mould parts havebeen fastened;

FIG. 4 is an isometric view of a finished prefabricated tubular withintegral moulded centraliser features according to one possibleembodiment (radial design); and

FIG. 5 is an isometric view of a finished prefabricated tubular withintegral moulded centraliser features according to another possibleembodiment (spiral design).

A prefabricated tubular having appropriate integral centralisingcapability is formed in the following way.

An OCTG tubular, e.g. a pipe 1 is prepared for application ofcentraliser parts by cleaning to remove possibly interferingcontamination such as paint, grease, oil, dust etc. A mould 2 having aplurality of suitable mould cavities 3 for forming projecting parts,e.g. radially extending blades 4, is presented around the tubular at asuitable axial position and fastened directly against the exteriorcurved surface of the tubular to provide a tight fit sufficient topermit a successful moulding operation. Various patterns of stand-offparts can be formed, e.g. as shown in FIGS. 4 (uniform radialpositioning) and 5 (spiral configuration).

A moulding composition, comprising composite resin materials loaded withhard particles is introduced into the mould cavities directly againstthe tubular wall, and the moulding operation is carried out to cure theMoulding composition.

The moulding composition in this case comprises a curable resin, ceramicparticulate filler materials, including optional chopped carbon fibrematerials. The commercially available PROGUARD CRB can be consideredsuitable for this purpose.

The composite material here is provided pre-moulding as separatetwo-part raw material components for admixing for moulding whereby thewhole can be reacted. The reaction may be catalytically controlled suchthat the various components in the separated two parts of the compositematerial will not react until they are brought together under suitablemoulding conditions. Thus the one part may include an activator, orinitiator, or catalytic component required to promote, initiate orfacilitate the reaction between the whole mixed composition. Theappropriate balance of components can be achieved in the mould by use ofpre-calibrated mixing and dosing equipment.

The properly mixed and dosed composition cures rapidly in the mouldwhich can then be released from around the tubular, leaving a pre-formedcentraliser bonded or fused to the outer surface of the tubular.

In use the pre-fabricated tubular with integral centraliser features isinstalled and used as for the prior art tubular plus centraliserassemblies, except that the user totally avoids the on-site assemblywork. A further advantage is that the user is able to free up storagespace normally reserved for the centraliser stock usually taking up deckspace separately from the pipe rack.

1. A prefabricated tubular body for use downhole, comprising: integralcentralizer formations, said formations being formed as projectionsmolded directly onto the tubular body from moldable materials comprisinga curable resin, ceramic particulate filler materials, and choppedcarbon fiber.
 2. A prefabricated tubular body according to claim 1,wherein the tubular body is formed by providing a resin-ceramiccomposite material of one of powders, particles, fibrils, choppedfibers, or beads, including fillers or other molding auxiliaries, andmeans for curing or setting the resin into a molded form on the tubularbody.
 3. A prefabricated tubular body according to claim 2, wherein saidmeans for curing or setting the resin comprises a mold, and the mold isutilized in a molded operation that comprises applying at least oneappropriately contoured molding part of the mold to a tubular body,loading the mold with resin-ceramic materials in predetermined amountsto form a desired composite, by injecting the materials into the mold,curing the materials in the mold, and removing any mold part to leave adesired molded part formed on the tubular body.
 4. A prefabricatedtubular body according to claim 1, wherein after removal of the any moldpart, the tubular body is coated with resins, paints, or land surfacefinishing agents.
 5. A prefabricated tubular body according to claim 2,wherein after removal of the any mold part, the tubular body is coatedwith resins, paints, or land surface finishing agents.
 6. Aprefabricated tubular body according to claim 3, wherein after removalof the any mold part, the tubular body is coated with resins, paints, orland surface finishing agents.
 7. A prefabricated tubular body accordingto claim 1, wherein the projections are located in uniform radialpositions on the tubular body.
 8. A prefabricated tubular body accordingto claim 1, wherein the projections are located in a spiralconfiguration on the tubular body.
 9. A prefabricated tubular bodyaccording to claim 1, wherein the moldable materials comprise a catalystto initiate curing of the curable resin.
 10. A prefabricated tubularbody according to claim 9, wherein the catalyst is thermally activated.11. A prefabricated tubular body according to claim 1, wherein thecurable resin is chemically activated by a curing initiator.
 12. Aprefabricated tubular body according to claim 1, wherein the curableresin, the ceramic particulate filler materials, and the chopped carbonfiber are mixed prior to being molded into the projections.
 13. Aprefabricated tubular body, comprising: the tubular body; and means forcentralizing the tubular body downhole, wherein the means forcentralizing include chopped carbon fiber and are molded directly to anoutside of the tubular body.
 14. A prefabricated tubular body accordingto claim 13, wherein the means for centralizing include projectionsmolded directly onto the tubular body from moldable materials comprisinga curable resin, ceramic particulate filler materials, and the choppedcarbon fiber.
 15. A prefabricated tubular body system, comprising: awell bore leading to oil or gas; and the tubular body positioned in thewell bore, wherein the tubular body includes integral centralizerformations, said formations being formed as projections molded directlyonto the tubular body from moldable materials comprising a curableresin, ceramic particulate filler materials, chopped carbon fiber.
 16. Aprefabricated tubular body system according to claim 15, wherein theformations are in direct contact with the well bore to centralize thetubular body.
 17. A method, comprising: mixing a composite materialincluding a curable resin, ceramic particulate filler materials, andchopped carbon fiber; adapting a tubular body to be inserted in a wellbore by attaching a mold to the tubular body; injecting the compositematerial into the mold on the tubular body to form centralizerprojections on the tubular body; and inserting the tubular body in thewell bore; and rotating the tubular body such that the centralizerprojections align the tubular body within the well bore.
 18. The methodaccording to claim 17, wherein the tubular body leads is an existingtubular body.
 19. The method according to claim 17, wherein the wellbore leads to oil or gas.
 20. The method according to claim 17, whereinthe centralizer projections are formed directly on an exterior surfaceof the tubular body.